From Molecular Clouds to Circumstellar Disks

Comets II ◽  
2004 ◽  
pp. 67-80
Author(s):  
Alan P. Boss
Keyword(s):  
Molecular Clouds ◽  
Circumstellar Disks

scholarly journals Mass Outflows Associated with Young Stellar Objects

1987 ◽  
Vol 115 ◽  
pp. 255-273
Author(s):  
Stephen E. Strom ◽  
Karen M. Strom
Keyword(s):  
Magnetic Field ◽  
Molecular Clouds ◽  
Circumstellar Disks ◽  
Young Stellar Objects ◽  
Molecular Flow ◽  
Birth Process ◽  
Stellar Objects ◽  
Molecular Outflows ◽  
Bolometric Luminosity ◽  
Field Geometry

The fundamental properties of optical and molecular outflows associated with young stellar objects are reviewed. Particular emphasis is placed on a discussion of new results concerning outflow energetics, collimating structures and the relationship between outflow properties and the magnetic field geometry characterizing their host molecular clouds. IRAS observations of YSO mass outflows reveal extended far-IR emission associated with high velocity molecular gas; in the case of L1551 IRS5, the luminosity of the extended emission is ∼10 times the mechanical luminosity inferred from observation of the molecular flow (and thus ≳0.1 the bolometric luminosity of the YSO driving the outflow). Circumstellar disks of size ∼100 au appear to be a common, if not certain outcome of the stellar birth process for stars of ∼1M⊙. In a few cases, it has been possible to resolve disk-like structures associated with YSO outflow sources. In such cases, the disk axes appear to lie along the direction of molecular outflows or stellar jets. The mass outflows (and by inference, the axes of circumstellar disks) show a remarkable tendency to align along the direction of the magnetic fields which thread their host molecular clouds. This suggests that the cloud magnetic field must play an important role in determining the flattening (and perhaps the rotation) of protostellar structures.

scholarly journals A First Look at the Disk Population in the Auriga-California Molecular Cloud

2013 ◽  
Vol 8 (S299) ◽  
pp. 151-152
Author(s):  
Hannah Broekhoven-Fiene ◽  
Brenda C. Matthews ◽  
Paul M. Harvey ◽  
Keyword(s):  
Grain Growth ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Planet Formation ◽  
Circumstellar Disks ◽  
The Other ◽  
Giant Molecular Clouds ◽  
Formation Potential

AbstractThe Auriga-California Molecular Cloud (AMC) is one of two nearby (within 500 pc) giant molecular clouds, the other being the Orion A Molecular Cloud (OMC). We aim to study the properties of circumstellar disks in the AMC to compare the planet formation potential and processes within the AMC to those for other clouds. A first look with measurements from Spitzer observations suggests that AMC disk properties, such as the distribution of disk luminosities and the evolution of the mid-IR excesses, are not vastly different from those in other regions. Follow-up observations in the submm, mm and cm can be used to measure disk masses and the degree of grain growth from spectral slopes to more completely characterize the disk population.

scholarly journals THE NATURE OF TRANSITION CIRCUMSTELLAR DISKS. II. SOUTHERN MOLECULAR CLOUDS

2012 ◽  
Vol 749 (1) ◽  
pp. 79 ◽  
Author(s):  
Gisela A. Romero ◽  
Matthias R. Schreiber ◽  
Lucas A. Cieza ◽  
Alberto Rebassa-Mansergas ◽  
Bruno Merín ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Circumstellar Disks

Astrochemical models of water

2015 ◽  
Vol 11 (A29B) ◽  
pp. 380-384
Author(s):  
Yuri Aikawa
Keyword(s):  
Molecular Clouds ◽  
Early Stage ◽  
Reaction Network ◽  
Network Models ◽  
Circumstellar Disks ◽  
Disk Surface ◽  
Water Ice ◽  
T Tauri ◽  
Deuterium Enrichment ◽  
Cloud Cores

AbstractWe will review the chemical reaction network models of water and its D/H ratio coupled with the dynamics of star formation. Infrared observations show that water ice is abundant even in molecular clouds with relatively low visual extinction (~ 3 mag), which indicates that water ice is formed in early stage of molecular clouds. We thus start from a possible formation site of molecular clouds, i.e. the converging flow of diffuse gas. Then we proceed to dense cloud cores and its gravitational collapse, during which a significant deuterium enrichment occurs. The gas and ice accrete onto the circumstellar disks, which evolve to protoplanetary disks in T Tauri phase. If the disks are turbulent, water could be photodissociated in the disk surface and re-formed in deeper layers. The cycle continues until the dust grains with ice mantle are decoupled from the turbulence and settle to the midplane. The water D/H ratio could thus vary within the disk.

scholarly journals Recent Developments in Simulations of Low-mass Star Formation

2010 ◽  
Vol 6 (S270) ◽  
pp. 65-72
Author(s):  
Masahiro N. Machida
Keyword(s):  
Star Formation ◽  
Numerical Simulations ◽  
Formation Process ◽  
Molecular Clouds ◽  
Circumstellar Disks ◽  
Mass Star ◽  
Star Forming ◽  
Protostellar Jets ◽  
Recent Developments ◽  
Low Mass

AbstractIn star forming regions, we can observe different evolutionary stages of various objects and phenomena such as molecular clouds, protostellar jets and outflows, circumstellar disks, and protostars. However, it is difficult to directly observe the star formation process itself, because it is veiled by the dense infalling envelope. Numerical simulations can unveil the star formation process in the collapsing gas cloud. Recently, some studies showed protostar formation from the prestellar core stage, in which both molecular clouds and protostars are resolved with sufficient spatial resolution. These simulations showed fragmentation and binary formation, outflow and jet driving, and circumstellar disk formation in the collapsing gas clouds. In addition, the angular momentum transfer and dissipation process of the magnetic field in the star formation process were investigated. In this paper, I review recent developments in numerical simulations of low-mass star formation.

The Infancy of Solar-Type Stars and its Relevance for the Origin of Life

1997 ◽  
Vol 161 ◽  
pp. 267-282 ◽  
Author(s):  
Thierry Montmerle
Keyword(s):  
Main Sequence ◽  
Solar Nebula ◽  
Circumstellar Disks ◽  
T Tauri Stars ◽  
Necessary Condition ◽  
Sequence Evolution ◽  
T Tauri ◽  
Solar Type ◽  
Optical Domain ◽  
The Origin Of Life

AbstractFor life to develop, planets are a necessary condition. Likewise, for planets to form, stars must be surrounded by circumstellar disks, at least some time during their pre-main sequence evolution. Much progress has been made recently in the study of young solar-like stars. In the optical domain, these stars are known as «T Tauri stars». A significant number show IR excess, and other phenomena indirectly suggesting the presence of circumstellar disks. The current wisdom is that there is an evolutionary sequence from protostars to T Tauri stars. This sequence is characterized by the initial presence of disks, with lifetimes ~ 1-10 Myr after the intial collapse of a dense envelope having given birth to a star. While they are present, about 30% of the disks have masses larger than the minimum solar nebula. Their disappearance may correspond to the growth of dust grains, followed by planetesimal and planet formation, but this is not yet demonstrated.

Structure of the turbulent atomic gas and formation of molecular clouds

2008 ◽  
Vol 31 ◽  
pp. 15-18
Author(s):  
P. Hennebelle ◽  
E. Audit
Keyword(s):  
Molecular Clouds ◽  
Atomic Gas
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